<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>Demo</title>
<script type="text/javascript">
function F_Open_dialog() 
{ 
document.getElementById("btn_file").click(); 
}
</script>
</head>
<body>
<div>
<input type="file" id="btn_file" style="display:none">
<button type="button" onclick="F_Open_dialog()">选择文件</button>
</div>
</body>
</html>